var nav = document.querySelectorAll('.nav li');
var main = document.querySelectorAll('.main ul li');
for(var i = 0; i < nav.length; i++){
	nav[i].index = i;
	nav[i].onmouseover = function(){
		for(var j = 0; j < nav.length; j++){
			nav[j].classList.remove('active');
			main[j].classList.remove('active');
		}
		this.classList.add('active');
		main[this.index].classList.add('active');
	}
}
